ProjectSummary This renewal application builds upon a productive collaboration between the Moore (biosynthesis/natural products chemistry) and Jensen (bioinformatics/microbiology) labs. It seeks to capitalize on the biosynthetic potential maintained in bacterial genomes by developing three specific areas of research: 1) Transcriptome guided natural product discovery, 2) Heterologous expression, production, and characterization of Salinispora secondary metabolites, and 3) Characterization and exploitation of secondary metabolite regulation. The research will be implemented using the model marine actinomycete genus Salinispora, for which a unique culture collection and a large number of genome sequences are available. Comparative transcriptomics will be used to distinguish between silentandexpressedgeneclusters,identifykeyregulatoryelementsassociatedwiththeirsilencing,and prioritize clusters for heterologous expression and product characterization. The resulting compounds will be isolated, characterized, and subjected to biological testing. A workflow has been developed to target gene clusters that possess the highest probability to yield structurally unique and biologically active compounds. The mechanistic enzymology associated with unique structural features will be interrogated and used to inform future structure predictions. This project will specifically address the regulation of secondary metabolism by testing the effects of salinipostin as an A-factor-like regulator, identifying the genetic basis for a spontaneous, pigment-less mutant that is reduced in secondary metabolite production, and introducing regulatory elements whose disruption has been linked to gene clustersilencinginspecificstrains.Thefundamentalgoalsaretodevelopnewtoolsandapproachesto identify the natural products encoded in bacterial genomes, obtain new information about the mechanistic biochemistry responsible for their assembly, and to develop more efficient approaches to minebacterialgenomesforthestructurallyuniqueandbiologicallyactivecompoundstheyencode.The research effectively combines the complimentary expertise of two research groups in the areas of marinemicrobiology,biosynthesis,andnaturalproductdiscovery.